1. Field of the Invention
This invention concerns a method of manufacturing soldering tips for use with electric soldering instruments, including automatic soldering or desoldering machines, as well as to such soldering tips.
2. Description of the Prior Art
Soldering tips for use with electric soldering instruments are generally made of copper metal which has good heat conductivity and excellent workability.
However, soldering tips made of copper tend to be eroded or consumed in frequent use by the attack of solder and/or flux under the high working temperature and this disadvantage has become remarkable in recent years as the soldering work has been employed in continuous line operation, in which articles supplied one by one, for example, on a belt conveyor at a considerable line speed have to be soldered successively. Particularly, in a case where the soldering work is applied to the accurate fabrication, for instance, of fine electronic components, the top ends of soldering tips, which may possibly be less than 1 mm in diameter, are readily consumed to necessitate frequent replace of the tips thereby worsen the working efficiency.
In view of the foregoings, the surfaces of the copper tips have often been plated with iron to about 50-500 .mu.m thickness in order to protect the tips against such undesired consumption.
In a conventional method of manufacturing an erosion resistant soldering tip of this type, a copper substrate is at first shaped into a desired tip configuration and then an iron layer is plated to a required thickness on the outer surface of the thus shaped copper blank.
In the iron plating process, however, since the current density in a plating bath is not uniform but centralized locally, for instance, at the top end and the edge portions of the copper substrate, the thickness of the resulted plated layer is increased unevenly in these portions, where the texture of the deposited iron is undesirably hard and brittle as well. In view of the above, the surface of the iron layer plated on the copper substrate is usually finished by cutting or grinding work, for instance, using lathe, milling machine, grinder or endless sand paper.
However, since the unevenness for the thickness of the electrically deposited layer can not exactly be recognized merely by its appearance, it is difficult to finish the plated layer into a uniform thickness with no scattering over the entire surface, which often results in defective final products having not uniform thickness and thus erosion resistance.
The above problem is particularly remarkable upon manufacturing a soldering tip having a top end of a fine diameter, in view of the plating process and the prefabrication work. In manufacturing a soldering tip whose top end has, for example, about 1 mm total diameter including the thickness of the plated iron layer of about 250 .mu.m, the actual diameter for the top end of the copper substrate should be 0.5 mm or less. However, such fine end of the substrate would easily be flexed or injured by being caught in the holes of a barrel wall to extremey reduce the product yield during plating process in a rotary barrel. This is also caused more or less in other plating units such as those using rack members. In addition, it is very difficult to fabricate the end of the copper substrate into various shapes with less than 0.5 mm in diameter by machining work, which brings about a problem in the mass production of such tips. For decreasing the uneven deposition of the iron layer it has thus been attempted to carry out the plating process for a longer time while using moderate plating conditions, but it is time-consuming and can not yet dissolve the foregoing problems completely.
For alleviating the difficulties involved in the manufacture and finishing of the iron-plated copper soldering tips, W. S. Fortune suggests in his U.S. Pat. No. 4,055,744, to assemble a soldering tip by the use of a copper core and an iron or steel cap by fitting the former into the latter and then shaping them together into a desired configuration by hammering, peening or the like as shown in FIG. 10 through FIG. 19 of the patent. However, in the Fortune's tip, since the copper core and the iron cap have to be fabricated separately by machining or the like in complementary shapes and then just fitted to each other, it may complicate the manufacturing step for the tip, particularly, of fine diameter as compared with the plating method. Thus, no effective means have hitherto been known for the improvement of iron-plated copper soldering tips.